Global mapper Latitude/Longitude config tutorial for ArmA 3 real world data terrains.

Load global mapper project, select user created feature grid.

RMB → crop combine/split/split functions → subdivide quadliteral area. Use grid number of rows and columns: 2, click OK. On modify feature info dialog click OK.

Drag a box around the new vertice in center of your user created feature grid, then RMB → vertex editing → set position of selected vertices.

Tick geographic coordinates (latitude/longitude).

Copy latitude to clipboard and goto latlong.net website, paste values to latitude box. Repeat this for longitude.

Note that this websites longitude seconds input box only accepts integers (full numbers, no XX.XXXXX).

Click convert to decimal degrees button and now you have two values, latitude and longitude.

For some reason arma3 latitude is with NEGATIVE number if its north of equator.

Now just copy-paste the calculated values from latlong.net website into your config and don't forget the north of equator negative value.

config.cpp

latitude = -14.98310431;
longitude = 43.21916667;